1. Field of the Invention
The present invention relates to an emitting light source apparatus for use in a reflecting optical encoder.
2. Description of the Related Art
Two types of optical encoder are known; the first is a transmission type; the second is a reflection type. The transmission type includes a scale, a light-emitting element and a light-receiving element. The scale has an optical grating formed along an axis of measurement. The light-emitting element and the light-receiving element are provided on opposite sides of the scale. In the transmission type, the light from the light-emitting element is applied to the scale and the light transmitted through the scale is received by the light-receiving element. In the reflection type, the light-emitting element and the light-receiving element are provided on one side of the scale, and the light from the light-emitting element is applied to the scale and the light reflected from the scale is received by the light-receiving element.
The reflection type can be constructed in a smaller size than the transmission type since the light-emitting element and the light-receiving element can be provided on one side of the scale. However, the current model of commercially available reflection-type optical encoder has a structure that requires precise positioning of the light-emitting and receiving elements. In addition, it needs a wiring board to form signal-carrying wires for these elements. Because of this complexity in structure, the size of the reflection-type optical encoder cannot be reduced to a satisfactory level.
In order to cope with this problem, the Applicant previously proposed the idea of using a resin block to realize a compact sensor head (U.S. Pat. No. 5,995,229). However, the demand for a further decrease in size and thickness is growing. Further, there is a need to develop an emitting light source apparatus capable of more precise detection.